The German Patent Application DE 10 2011 080 431 A1 discusses a braking system for a vehicle. The braking system includes at least one admission pressure sensor that is adapted for determining a pressure prevailing in the master brake cylinder.
FIGS. 1a and 1b show coordinate systems for clarifying deviations between commonly measured admission pressure values, sensor values processed in accordance with the related art, and pressure values prevailing in a master brake cylinder. The abscissas of the coordinate systems of FIGS. 1a and 1b are the time axis t (in seconds), while the ordinates of the coordinate systems of FIGS. 1a and 1b indicate a pressure (in bar).
A graph g in FIG. 1a shows commonly measured admission pressure values, while a graph g0 in FIG. 1a indicates the (real) pressure values/real admission pressure values prevailing in the master brake cylinder. Graph g reveals that a signal noise typically occurs. The signal noise can be eliminated by a sensor signal conditioning, whereby a graph g′, which includes sensor values processed in accordance with the related art, can be derived from graph g. A suitable sensor signal conditioning lasts, however, for at least a signal conditioning time Δt. However, during signal conditioning time Δt, the pressure/real admission pressure prevailing in the master brake cylinder can change by a pressure difference Δp.
FIG. 1b shows an attempt to use an extrapolation in accordance with the equation (Equation 0)p0=p′+a·Δt,  (Equation 0)
to estimate a likely admission pressure p0 on the basis of processed sensor values p′ of graph g′ and a slope a of processed sensor values of graph p′.